CVE Intelligence
High Memory corruption

CVE-2025-0689 — Grub2: udf: heap based buffer overflow in grub_udf_read_block() may lead to arbitrary code execution

When reading data from disk, the grub's UDF filesystem module utilizes the user controlled data length metadata to allocate its internal buffers. In certain scenarios, while iterating through disk sectors, it assumes the read size from the disk is always smaller than the allocated buffer size which is not guaranteed. A crafted filesystem image may lead to a heap-based buffer overflow resulting in critical data to be corrupted, resulting in the risk of arbitrary code execution by-passing secure boot protections.

Published Mar 3, 2025 · Updated Oct 21, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: redhat

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.5% (30-day exploitation probability)+6
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.5%
ahead of 42% of scored CVEs · Oct 26, 2026
Affects
Gnu
Grub2
CVSS base
7.8
High · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Gnu Grub2).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Gnu Grub2 ≤ 2.12 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
7.8 CVSS 3.1 High 1.8 5.9 secalert@redhat.com via NIST National Vulnerability Database
7.8 CVSS 3.1 High 1.8 5.9 nvd@nist.gov via NIST National Vulnerability Database
7.8 CVSS 3.1 High — — redhat via CVE Program (cve.org) e CISA ADP
6.4 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H (score shown at the top: secalert@redhat.com)
Sources disagree significantly and the divergence is under review. Every score is kept with its origin. For prioritization we use 7.8 (secalert@redhat.com via NIST National Vulnerability Database) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-120 · Classic Buffer Overflow

Other CVEs with this weakness →

EPSS over time FIRST

Oct 21, 2026 → Oct 26, 2026 · 6 reading(s) · max 0.50%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 21, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 21, 2026
  • Affected products added · gnu/grub2
    Oct 21, 2026 · NIST National Vulnerability Database
  • CVSS changed · 7.8
    Oct 21, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 21, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 21, 2026 · Alertas do Telegram
  • 2025
  • CVE published
    Mar 3, 2025 · redhat

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 21, 2026 – Oct 21, 2026
  • 1× Official description updated · Oct 21, 2026 – Oct 21, 2026

References

5 on the record

Elsewhere on this site

Gnu
every CVE for this vendor
Memory corruption
same class
CWE-120
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-97876 Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address 25d
  • CVE-2025-61662 Grub2: missing unregister call for gettext command may lead to use-after-free Nov 18, 2025
  • CVE-2025-61663 Grub2: missing unregister call for normal commands may lead to use-after-free Nov 18, 2025
  • CVE-2025-61664 Grub2: missing unregister call for normal_exit command may lead to use-after-free Nov 18, 2025
  • CVE-2025-54770 Grub2: use-after-free in net_set_vlan Nov 18, 2025
  • CVE-2025-54771 Grub2: use-after-free in grub_file_close() Nov 18, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-0689 is "Grub2: udf: heap based buffer overflow in grub_udf_read_block() may lead to arbitrary code execution", rated High. It affects Grub2 (Gnu); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. EPSS 0.50% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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